New-look Chelsea are a bit of a mystery for Dortmund coach Terzic

Borussia Dortmund will be facing a new-look Chelsea in their Champions League last 16 first leg on Wednesday following the English club's big spending spree but coach Edin Terzic said on Tuesday his team was ready for any surprises.

Chelsea signed more than half a dozen players in the January transfer window including British record capture Enzo Fernandez for more than $130 million, and Benoit Badiashile, Noni Madueke, Andrey Santos, David Fofana and Mykhailo Mudryk among others.

They spent more than $350 million in January alone while also bringing in Portugal international Joao Felix on loan.

"It is not easy to analyse (Chelsea)," Terzic told a news conference. "After the Champions League draw we watched their games but then in the transfer window there was so much movement from them.

"They sold key players, brought in other key players. Then we saw the official Champions League list but then there was the transfer of Joao Felix, for example," Terzic added.

"So you don't know how they will play. In defence they played with four but before also with three in the back. We will prepare for everything."

The Germans have enjoyed a perfect start to the year, winning all five of their league matches so far, including Saturday's 2-0 victory over hosts Werder Bremen.

The Ruhr valley club has also been banking on youth, with teenagers having scored 15 league goals this season, as many as all the other Bundesliga teams combined.

But one of them, forward Youssoufa Moukoko, will be missing on Wednesday, having been ruled out for six weeks following his knee ligament injury on Saturday.

"We need at least one win against Chelsea. Obviously it is easier here with 80,000 to create euphoria. But we need two good performances and we will try to deliver," Terzic said.

"It wont be an easy task because we know with what kind of quality they are coming here. It is a top team that got top reinforcements in the winter so we need an outstanding performance."